Abiotic and Biotic Components in Ecosystems Source: Jones, M and G. Jones 1995 Biology. Cambridge University Press. United Kingdom

Abiotic and Biotic Factors Abiotic: Non-living components of the ecosystem Physical Chemical Biotic: Living components Biotic interactions Biotic indexes

Studying Abiotic Factors

Abiotic Physical Factors pH (of soil and water): important factor in the process of absorption of nutrients from the soil. Acidic soils inhibit absorption and decreases biological diversity. Salinity: amount of dissolved salts. This factor has an effect on the absorption of H 2 O by osmosis. Some plants are adapted to soil with high salinity Climate: influences natural populations The two most important factors are temperature and precipitation

Temperature: temperatures higher than optimum denature enzymes; low temperatures inactivate enzymes. Has negative effects on growth, productivity and reproduction Water (precipitation): Needed for vital activities (enzyme activity, transport, photosynthesis, support) Light (intensity and duration): Important for photosynthesis, flowering, reproduction, phototropism. In dark areas of the world where there is low light intensity and duration

Abiotic Chemical Factors  Soil: affects plants and therefore animals. Plants rely on it for many of their requirements Provides: anchorage, nutrient minerals, water, air; habitat  Oxygen: needed by most living organisms. Can quite often be in short supply in water (in riffles there is large supply; in pools is sometimes depleted due to decomposition BOD (biochemical oxygen demand) DO (dissolved oxygen)

 Nutrients Phosphorus  Mineral Nutrients: Plants need a continuous supply of nutrients from the soil for manufacturing enzymes, proteins, vitamins, nucleotides and other compounds Phosphorus Mg Fe

Studying Biotic Factors

Biotic Factors Include descriptions of the following factors: Availability of food Predators Parasites Competition Biotic Indexes Abundance or Pop. Size (random sampling) Density (# of organisms per area or volume) Biological diversity (biodiversity index) Distribution (type): Random Clumped Uniform

Studying biotic components of ecosystems Random sampling: Using randomly selected representative samples. Including a large portion (sample) of the population Random Sampling using Quadrats: It can be any size, but one with sides of about 0.5 m is convenient in the field Transects: Allows us to see distribution of organisms in the field. A line crossing the field. A long calibrated line or tape could be used to record all plants/organisms touching the field or at certain intervals Mark-release-recapture: Use with animals that move around a lot.

Classification and Identification of Organisms Why do we classify? To identify organisms To make inferences about characteristics To establish evolutionary links How do we name organisms? Binomial System

Five Kingdoms Prokaryota Protoctista Fungi Plantae Animalia

Classification from species to Kingdom HUMANBLUE WHALE Kingdom AnimaliaAnimalia Phylum ChordataChordata Class MammaliaMammalia Order VertebrataCetacea Family HominidaeBalaenopteridae Genus HomoBalaenoptera species sapiensmusculus

Evidence used in classification Fossil record Biochemical evidence Anatomical Structures Geographical Distribution

Identifying Organisms Dichotomous or Taxonomic Key Practice: Taxonomic Key for snakes and for salamanders